US5818177A - Variable-reluctance synchronous electric linear actuator - Google Patents

Variable-reluctance synchronous electric linear actuator Download PDF

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Publication number
US5818177A
US5818177A US08/777,050 US77705096A US5818177A US 5818177 A US5818177 A US 5818177A US 77705096 A US77705096 A US 77705096A US 5818177 A US5818177 A US 5818177A
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US
United States
Prior art keywords
piston
plates
stator
elements
linear actuator
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Expired - Fee Related
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US08/777,050
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English (en)
Inventor
Michel Amiet
Jean Lucidarme
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Direction General de lArmement DGA
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Delegation Generale pour lArmement
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Assigned to ETAT FRANCAIS REPRESENTE PAR LA DELEGUE GENERAL POUR L'ARMEMENT reassignment ETAT FRANCAIS REPRESENTE PAR LA DELEGUE GENERAL POUR L'ARMEMENT ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: AMIET, MICHEL, LUCIDARME, JEAN
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K41/00—Propulsion systems in which a rigid body is moved along a path due to dynamo-electric interaction between the body and a magnetic field travelling along the path
    • H02K41/02—Linear motors; Sectional motors
    • H02K41/03—Synchronous motors; Motors moving step by step; Reluctance motors
    • H02K41/031—Synchronous motors; Motors moving step by step; Reluctance motors of the permanent magnet type
    • H02K41/033—Synchronous motors; Motors moving step by step; Reluctance motors of the permanent magnet type with armature and magnets on one member, the other member being a flux distributor
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K2207/00—Specific aspects not provided for in the other groups of this subclass relating to arrangements for handling mechanical energy
    • H02K2207/03—Tubular motors, i.e. rotary motors mounted inside a tube, e.g. for blinds

Definitions

  • the present invention relates to a variable-reluctance synchronous linear electrical actuator and relates, in particular, to an electrical linear actuator of the type having a stator and a piston, both of which have elements in a form of plates or teeth disposed parallel to the direction of displacement of the piston.
  • actuators there are three types of actuators, namely, hydraulic, pneumatic and electrical actuators.
  • linear actuators there are already linear actuators that are either a pure variable-reluctance type or a hybrid variable-reluctance type (i.e., those that use magnets for excitation). Electrical actuators have far less thrust than the pneumatic or hydraulic actuators. However, there are linear electrical actuators with a strong thrust that use electromagnets, in which, due to their design, the thrusting force is a result of a normal component of the magnetic field. However, this strong thrust is possible over only short distances.
  • electrical actuators cannot compete with pneumatic actuators (and still less with hydraulic actuators) because, when electrical actuators have a high specific thrust, they traverse only short distances. It would, therefore, be useful to obtain electrical actuators with capacities at least similar to those of pneumatic actuators because, unlike compressed air, electricity allows very precise positioning and flexibility in control and, hence, movement.
  • variable-reluctance actuator has a stator and a piston having a core bearing thin ferromagnetic blades that are parallel to each other and parallel to the direction of movement of the piston.
  • Each of the thin ferromagnetic blades is divided in a lengthwise direction, i.e., in the direction of movement of the piston, into blocks with a specified pitch.
  • the ferromagnetic circuit of each winding also has several thin blades alternating with those supported by the core which are also divided into blocks with the same pitch as that of the blocks of the core blades.
  • this pure variable-reluctance actuator has drawbacks.
  • a hybrid variable-reluctance actuator that is, an electrical linear actuator having permanent magnets.
  • an object of the present invention is to obtain an electrical actuator of the type having a stator and a piston with performance capabilities comparable to those of pneumatic actuators, particularly ones having a strong thrust or an acceleration over a long distance.
  • Another object of the present invention is to provide an electrical actuator that has no "end effect” and minimal friction when the piston moves.
  • Yet another object of the present invention is to provide an electrical actuator that is simple to manufacture.
  • an electrical linear actuator includes an assembly and a structure.
  • An electrical linear actuator includes a stator assembly and a piston structure.
  • the stator assembly includes a casing having a bore extending therethrough and about a longitudinal axis, a winding structure disposed within the bore and in contact with the casing and a plurality of stator elements connected to the winding structure and arranged circumferentially in a plurality of rows extending parallel to the longitudinal axis within the bore and disposed apart from one another to form longitudinally extending channels between adjacent ones of the rows.
  • Each of the stator elements extends radially inwardly from the winding structure toward the longitudinal axis.
  • the piston structure includes a shaft extending along the longitudinal axis and has an outer cylindrical surface and a plurality of piston elements arranged circumferentially in a plurality of rows extending parallel to the longitudinal axis. Each of the piston elements is connected to the outer cylindrical surface of the shaft and extends radially outwardly therefrom relative to the longitudinal axis.
  • the piston structure is sized and adapted to be slidably received by and linearly movable within the stator assembly with each piston element being disposed within a respective one of the channels so that a gap is formed between facially opposing surfaces of the stator elements and the piston elements.
  • one of the plurality of stator elements and piston elements is ferromagnetic and the other one of the plurality of stator elements and the piston elements is non ferromagnetic.
  • each one of the plurality of the stator elements and the piston elements which are non ferromagnetic includes a plurality of magnets.
  • the plurality of magnets includes a first group of magnets having a first polarity and a second group of magnets having a second polarity different from the first group of magnets.
  • Individual ones of the magnets extend along the surface of the plurality of the stator elements and the piston elements which are non ferromagnetic in a direction parallel to the longitudinal axis.
  • the plurality of magnets are arranged whereby adjacent ones of the magnets have a different polarity.
  • Each row of the stator elements and the piston elements can be either an elongated plate or a plurality of teeth spaced apart from each other in a direction parallel to the longitudinal axis to form a slot between consecutive ones of the teeth. It is preferred that when adjacent rows of at least one of the stator elements and the piston elements is a plurality of teeth, the plurality of teeth are arranged in a manner whereby the teeth of adjacent rows are offset from one another. Preferably, when the teeth of adjacent rows are offset from one another, each of the plurality of teeth of one row is disposed centrally and opposite to a corresponding slot in the adjacent row of the plurality of teeth.
  • at least each one of a plurality of stator elements and the piston elements is configured in cross-section as a trapezoid.
  • FIG. 1 is a partial perspective view of a drawn stator, a component of the present invention
  • FIG. 2 is a perspective view of a plate shown in FIG. 1;
  • FIG. 3 is a partial perspective view of a piston, a component of the present invention.
  • FIG. 4 is a perspective view of a pair of piston segments and a pair of washers.
  • FIG. 5 is a side view in elevation of an actuator of the present invention.
  • a stator assembly 1 is composed of stator elements in a form of a set of plates 3 of equal lengths made of a non ferromagnetic material.
  • the plates 3 are disposed apart from one another and are regularly distributed over a matrix 4 having a tubular shape whose axis "A” corresponds to that of a piston structure or piston 2, shown in FIG. 3, and whose thickness "t” corresponds to the height "h” of the plates 3.
  • Axis "A" extends in a longitudinal direction.
  • the plates 3 have a trapezoidal cross-sectional configuration.
  • the plates 3 are surrounded by a winding structure 5 that generates an induced magnetic field.
  • the winding structure 5 is itself surrounded by a ferromagnetic casing 6.
  • the stator assembly 1 comprises a plurality of plates 3, the winding structure 5, and the casing 6 and is attached at each of its two ends to a ferromagnetic flange, not shown, in the shape of a crown. This configuration allows the piston 2 to slide inside the stator assembly in the longitudinal direction.
  • a plurality of magnets 15 are inserted into each of the plates 3 forming a jacket such that the polarity of the magnets 15 alternates in the lengthwise direction "l" corresponding to the direction of displacement of the piston.
  • the polarity of the magnets 15 is normal to the lengthwise direction "l" of the plates 3.
  • the distance between two magnets of the same polarity in the lengthwise direction "l” defines a pitch "p" of an actuator 20 (shown in FIG. 5).
  • They can be inserted by gluing in pre-cut holes, by casting, or by any other means.
  • the winding structure 5 is associated with a power supply circuit that can have a source of direct current and a chopper providing the winding structure 5 with cyclic pulses synchronized with the displacement, with the chopper possibly being controlled by a piston displacement sensor.
  • the piston 2 shown in FIG. 3 has a cross-sectional shape of a star with a plurality of arms 9 1 , 9 2 . . . 9 n .
  • Each arm 9 1 . . . 9 n of the star is composed of teeth 7 arranged along the pitch "p" of the actuator 20 and whose length “lt” (in the direction of displacement of the piston) is slightly less than pitch "p", for example, approximately 80% of the pitch.
  • the distance "d" of a slot 12 formed between consecutive ones of the teeth is hence, in this example, approximately 20% of pitch "p".
  • the teeth 7, made of ferromagnetic material, are attached to an outer cylindrical surface of a shaft 8 made preferably of nonmagnetic material, or even of insulating material especially if the piston 2 is designed to move rapidly.
  • teeth 7 of two adjacent arms are not opposite each other but offset such that the center of symmetry of one tooth 7 of, for example, arm 9 1 is opposite the center of a corresponding slot 12 between two consecutive teeth of arm 9 2 .
  • a distance "da” between two consecutive arms, for example, 9 1 and 9 2 , is slightly greater than the thickness "tp" of one plate 3 of the stator assembly 1, as shown in FIG. 1, thus constituting a set of air gaps "a” which can be large, in this case on the order of a millimeter.
  • piston 2 when assembled, piston 2 can slide in the stator assembly 1 along the longitudinal axis "A".
  • the staggered tooth design can be obtained advantageously by the assembly of identical piston segments 10 1 and 10 2 having a shape of a toothed wheel.
  • Each of these toothed wheels has one-half the number of teeth 7 as the piston 2 has arms 9.
  • the distance between two adjacent arms, for example, 9 1 and 9 2 of a piston segment 10 1 or 10 2 is equal to the sum of the width of one tooth, twice the thickness of plates 3 of the stator assembly 1 and the sets of air gaps "a".
  • the piston 2 is made by attaching to a washer 11 between a succession of piston segments 10 1 and 10 2 .
  • the piston segments 10 1 and 10 2 being disposed such that the center of symmetry of one tooth 7 of first piston segment 10 1 is opposite the center of symmetry of a space separating two successive teeth of piston segment 10 2 .
  • the lengthwise spacing between the teeth 7 of two consecutive arms 9 1 and 9 2 is effected by the washer 11.
  • the piston segments 10 1 and 10 2 can, for example, be made by casting.
  • a length "lp" of the piston 2 is greater than a length "ls" of the stator assembly 1 and, more precisely, that of the hollow cylinder limited by the two flanges.
  • bushings with balls can be used, placed between the stator assembly and the piston 2, outside the cylinder delimited by the flanges.
  • Angular positioning of the piston 2 relative to the stator assembly 1 can advantageously be effected by using guide arms connected to the piston 2 and sliding in adjustable slides attached to the stator and having ball bearings.
  • stator assembly and the piston would stick to each other.
  • stator plates all have the same environment, due to their cylindrical distribution, which eliminates any end effect and facilitates angular positioning because of the possibility of using large air gaps.
  • the actuator described is of the single-phase type.
  • a multi-phase actuator could easily be made, with n phases, by disposing several stator elements with an out-of-phase excitation of T/n along the piston, where T is the period of time of the supply current and n the number of phases.
  • each stator element must have the same pitch, the pitch of the actuator, which is also the pitch of the piston.
  • the positions of the stator elements must be such that, relative to the piston teeth, when the magnets of the first stator element coincide, those of the second stator element are offset by p/n, where p is the pitch of the actuator, those of the third stator element, if any, are offset by 2 p/n, etc.
  • the source elements of the magnetic field are all in the stator assembly.
  • an actuator according to the invention can function like a piston accelerator, and the latter can then become a projectile. Under these conditions, the actuator is an electrical launcher whose acceleration is conditioned by the order of ignition of the phases of the stator elements.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Electromagnetism (AREA)
  • Power Engineering (AREA)
  • Reciprocating, Oscillating Or Vibrating Motors (AREA)
  • Linear Motors (AREA)
US08/777,050 1995-12-29 1996-12-30 Variable-reluctance synchronous electric linear actuator Expired - Fee Related US5818177A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9515703 1995-12-29
FR9515703A FR2743217B1 (fr) 1995-12-29 1995-12-29 Accelarateur ou actionneur lineaire

Publications (1)

Publication Number Publication Date
US5818177A true US5818177A (en) 1998-10-06

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Application Number Title Priority Date Filing Date
US08/777,050 Expired - Fee Related US5818177A (en) 1995-12-29 1996-12-30 Variable-reluctance synchronous electric linear actuator

Country Status (4)

Country Link
US (1) US5818177A (fr)
EP (1) EP0783202B1 (fr)
DE (1) DE69616492T2 (fr)
FR (1) FR2743217B1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5942833A (en) * 1998-09-29 1999-08-24 Tokyo Parts Industrial Co., Ltd. Flat coreless vibrator motor
US20070267925A1 (en) * 2006-05-19 2007-11-22 Kevin Allan Dooley Fault monitoring of electric machines

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112187010B (zh) * 2020-10-22 2021-07-02 华中科技大学 一种同性极永磁直线同步电机

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2198299A1 (fr) * 1972-09-06 1974-03-29 Denis Michel
EP0004995A1 (fr) * 1978-04-17 1979-10-31 IMC Magnetics Corporation Dispositif linéaire et rotatif
EP0218521A1 (fr) * 1985-09-27 1987-04-15 Centre National De La Recherche Scientifique (Cnrs) Moteur électrique polyphasé à réluctance variable
EP0291638A2 (fr) * 1987-03-26 1988-11-23 International Business Machines Corporation Actionneur linéaire
EP0348851A1 (fr) * 1988-07-01 1990-01-03 Phase S.R.L. Moteur linéaire à force de poussée longitudinale élevée

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2588131A1 (fr) 1985-09-27 1987-04-03 Centre Nat Rech Scient Machine electrique tournante a reluctance variable polyentrefers
FR2588133A1 (fr) * 1985-09-27 1987-04-03 Centre Nat Rech Scient Moteur electrique polyphase a reluctance variable

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2198299A1 (fr) * 1972-09-06 1974-03-29 Denis Michel
EP0004995A1 (fr) * 1978-04-17 1979-10-31 IMC Magnetics Corporation Dispositif linéaire et rotatif
EP0218521A1 (fr) * 1985-09-27 1987-04-15 Centre National De La Recherche Scientifique (Cnrs) Moteur électrique polyphasé à réluctance variable
EP0291638A2 (fr) * 1987-03-26 1988-11-23 International Business Machines Corporation Actionneur linéaire
EP0348851A1 (fr) * 1988-07-01 1990-01-03 Phase S.R.L. Moteur linéaire à force de poussée longitudinale élevée

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5942833A (en) * 1998-09-29 1999-08-24 Tokyo Parts Industrial Co., Ltd. Flat coreless vibrator motor
US20070267925A1 (en) * 2006-05-19 2007-11-22 Kevin Allan Dooley Fault monitoring of electric machines
US7696657B2 (en) * 2006-05-19 2010-04-13 Pratt & Whitney Canada Corp. Fault monitoring of electric machines

Also Published As

Publication number Publication date
FR2743217A1 (fr) 1997-07-04
DE69616492T2 (de) 2002-06-27
DE69616492D1 (de) 2001-12-06
FR2743217B1 (fr) 1998-02-13
EP0783202A1 (fr) 1997-07-09
EP0783202B1 (fr) 2001-10-31

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